The circuits that are not adjustable can be made almost infinitely adjustable with a metering block change and/or a little drill and tap.
It's a rabbit hole
Yes, it is, but it's worth the trouble to have a clean idle and cruise. I changed the plugs in my 434 two years ago right before the Moparty at Bowling Green, the plugs in it had been there for three years and looked good. I have them in a bag for back up.
